Driving device

ABSTRACT

A shaft locking device for a motor-driven, hand-guided work tool spindle has a driven member fixedly connected thereto, a freewheel with locking members, a ring fixedly connected to the housing and engaged by the locking members in both rotating directions, a drive member coaxially arranged to the spindle with unlocking members cooperating with locking members releasing when the driving member is engaged, thereby releasing the driven member from the ring. Drive member cams are spatially separated from unlocking members wherein they penetrate the locking member. Driven members have catch openings such that both drive and driven members also have torque-transmitting catch surfaces for a motor-driven action of the spindle so that the catch surfaces have a larger distance from one another in a neutral position of the drive member than between the unlocking members and the locking members.

BACKGROUND OF THE INVENTION

The invention relates to a shaft locking device for the spindle of amotor-driven, hand-guided work tool.

A shaft locking device of the aforementioned kind is described in U.S.Pat. No. 3,243,023 which comprises a drive member with four unlockingelements for the locking members of a freewheel and where the unlockingelements are simultaneously designed as cams for engaging a drivenmember. The torque-transmitting surfaces of the cams and the drivenmember are designed to be very small in this solution and they are,therefore, subject to wear.

It is an object of the invention to create a shaft locking device forthe spindle of a motor-driven, hand-held work tool that has a longservice life.

SUMMARY OF THE INVENTION

Due to the spacial separation of unlocking elements and cams, there isspace for sufficiently dimensioned torque-transmitting drive surfaceswhich are practically not subject to any wear.

Because of the one-piece design of the spindle and its penetration ofthe drive member and the driven member, it has a simple design and astable support. This support of the spindle in connection with a looselydimensioned support of the drive member on the spindle contributes tothe long service life and the efficiency of the work tool, particularlyif the drive member is embodied as a toothed wheel. When its teeth aremade of plastic, there are noise-related advantages.

Because the axial cams penetrate the catch openings, the entire torquetransferring drive surfaces are always active, even in the event ofaxial mounting deviations of the spindle.

Because of the positioning of the unlocking members and of the cams,manufacturing advantages exist for turning and milling the drive member.The cams can axially or radially penetrate or extend into the catchopenings.

The deep-drawing or extruding of the driven member offers alsoadvantages in regard to manufacturing the cams for the locking membersand to flattening of the hub. The driven member can also be embodied asa thick disc which is preferably made of sintered steel. This realizes aparticularly low wear and safe operation of the shaft locking device.The number of the locking members depends on the magnitude of theoperational load.

The fixedly driven closing ring serves to limit the axial movement ofthe locking members of the free wheel and, thereby, its noisedevelopment. This is particularly important with hammer devices. In thecase of different length ratios, the fixedly driven closing ring can besubstituted by a standardized disc and, in the event that no hammerdevice is present, it can even be left out.

Advantageously, the cam surfaces of the cams are radially aligned withthe drive surfaces of the catch openings. This provides favorable torquetransmission and wear conditions.

A particularly torsionally strong connection between the driven memberand the spindle is achieved when the driven member is positive-lockinglyconnected to the spindle.

Advantageously, the driven member is force-lockingly connected to thespindle. This can be achieved by a press fit, for example. Thereby, aslip-clutch-like slip between the driven member and the spindle ispossible on an extreme load acting on the spindle so that a destructiondue to breaking-stress can be avoided.

BRIEF DESCRIPTION OF THE DRAWINGS

More features can be taken from the further claims. The drawingsschematically illustrate the embodiments of the invention which aredescribed in the following. It is shown in:

FIG. 1 a longitudinal section of the shaft locking device,

FIG. 2 a cross-section of the shaft locking device,

FIG. 3 a longitudinal section of another shaft locking device,

FIG. 4 a cross-section of another shaft locking device,

FIG. 5 a longitudinal section of a preferred further embodiment of theshaft locking device,

FIG. 6 a cross-section of the preferred further embodiment of the shaftlocking device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 and 2 show a spindle 1 with a thread 29 for the drill chuck anda ball bearing 2 as well as a drive member 3 and a driven member 4.

The interior ring of the ball bearing 2 is axially supported on ashoulder 6 of the spindle 1 by a locking ring 5. A second bearingprovided at the driving end of the spindle 1 is not illustrated.

The driving member 3 consists of a toothed wheel 7 that has an endgearing and is supported on the spindle 1. The toothed wheel 7 isaxially fixed with axial play by a further locking ring 8 and a shoulder9 of the spindle 1. For noise-related reasons, the gearing can becomprised of plastic. At the end face of the toothed wheel 7 facing thedriven member 4, three unlocking members 10 and three axial cams 11 arearranged in pairs concentrically with respect to one another. The threepairs each have a common center line 12, and neighboring center lines 12are provided at equal spacings.

The driving member 3 can also be embodied as a planetary gearing and beprovided with a two-position gear box.

The driven member 4 is provided with a deep-drawn, pot-shaped sheetmetal member 13, whose hub 14 is fixedly connected to the spindle 1 bytwo flattened portions 15. The hub 14 can also be fixedly connected tothe spindle 1 by a press fit or other kind of frictional connection orby positive locking. In the wall 16 of the sheet metal member 13 facingthe drive member 3, three catch openings 30 embodied as ring segments 17are provided which are radially engaged with rotary play by the threeaxial cams 11 of the toothed wheel 7. The cam surfaces 18 and drivesurfaces 19 of the sheet metal member 13, which face one another in thedirection of rotation, are radially aligned and are positioned oppositeone another with a clearance.

The sheet metal member 13 is provided with an outer ring-shaped wall 20having an outer shape that is embodied as cams 21 for the lockingmembers 22. The locking members 22 are positioned as pairs in the areabetween the catch openings 30 and are arranged between the outer wall 20and a ring 23 fixedly attached to the housing. The locking members 22are being pressed apart by spring elements 24 (for example, metal orplastic springs) and are held in a clamping position on the cams 21. Thecams 21, the locking members 22, and the ring 23 attached to the housingtogether form a freewheel 28. The number of the locking member pairs isdependent on the operational torque to be expected.

The unlocking members 10 embrace the outer, ring-shaped wall 20 of themetal member 13 at a spacing. They are provided at their end faces 25facing the locking members 22 a shaped surface matching the lockingmembers 22. The distance between the shaped surface and the lockingmembers 22 is smaller than the one between the cam surfaces 18 and thedrive surfaces 19.

The ring 23, fixedly attached to the non-represented housing of the worktool, is positive-lockingly connected, for example, by a toothed ring26.

The sheet metal member 13 is provided at the side facing away from thedriven member 4 with a closing member 27 that is fixedly connected tothe spindle 1 and limits the axial movement of the locking members 22and, thereby, the resulting noise development. This is particularlyimportant with hammer devices. If this is missing, the closing member 27can be eliminated.

FIGS. 3 and 4 illustrate another version of the shaft locking device.The same parts carry the same designation as in FIGS. 1 and 2, analogousparts carry a designation extended by an “a”.

In this version, differently designed cams 11 a of a differentlydesigned toothed wheel 7 a of a differently designed drive member 3 aengage with play corresponding radial recesses 17 a of an extrudedmember 13 a belonging to a differently designed driven member 4 a. Thisextruded member 13 a is fixedly connected to a different spindle 1 a.

At the circumference of the extruded member 13 a, between the radialrecesses 17 a, cams 21 (according to FIGS. 1 and 2) are provided thatcan be connected by locking members 22 to the ring 23 fixedly attachedto the housing. The locking members 22 are held axially by a closingmember 27 a that is connected to the differently designed cams 11 a.

The torque of the drive motor is transmitted by differently designed camsurfaces 18 a to differently designed drive surfaces 19 a of theextruded member 13 a.

Differently designed unlocking members 10 a embrace the extruded member13 a at a spacing. The distance between the differently designed endsurfaces 25 a of the differently designed unlocking members 10 a facingthe locking members 22 and the locking members 22 is smaller thanbetween the differently designed cam surfaces 18 a and the differentlydesigned drive surfaces 19 a of the extruded member 13 a.

FIGS. 5 and 6 illustrate another preferred embodiment of the shaftclamping device. The same parts carry the same designation as in FIGS. 1and 2, analogous parts carry a designation extended by a “b”.

In this embodiment, the cams 11 b of a different toothed wheel 7 b aresimilarly designed as the cams 11 a shown in FIGS. 4, wherebydifferently designed cam surfaces 18 b of the cams 1 b are approximatelyradially aligned with different drive surfaces 19 b of the catch opening30. These are embodied as differently designed radial recesses 17 b. Thecams 11 b project radially and axially with a play into thecorresponding recesses 17 b of a differently designed driven member 4 bwhich is embodied as a thick disc 13 b. The driven member 4 b isprovided with a different hub 14 b which is fixedly and force-lockinglyconnected to a different spindle 1 b by press fit.

At the circumference of the disc 13 b dovetailed cams 21 according toFIGS. 1 to 4 are provided between the radial recesses 17 b. The cams 21can be connected to the ring 23, fixedly attached to the housing, bylocking members 22. The locking members 22 are held axially by adifferently designed closing member 27 b which is fixedly connected tothe spindle 1 b.

The torque of the drive motor is transmitted by different cam surfaces18 b to different drive surfaces 19 b of the disc 13 b.

Different unlocking elements 10 b embrace the disc 13 b at a spacing.The distance to the end surfaces 25 of the unlocking members 10 b facingthe locking members 22 is smaller than between the different camsurfaces 18 b and the different drive surfaces 19 b of the disc 13 b. Inthis embodiment, the locking members 22 rest against the correspondingends 25 of the different unlocking members 10 b, due to the springaction of the spring element 24 arranged between them.

The illustrated shaft locking devices operate as follows:

On operation of the motor, the toothed wheel 7, 7 a, 7 b is rotated onthe spindle 1, 1 a, 1 b. Thereby, first, the first locking elements 22as viewed in the direction of rotation are shifted into the recess ofthe cams 21 by the unlocking members 10, 10 a, 10 b and are therebyunlocked. Only then, the cam surfaces 18, 18 a, 18 b engage the drivesurfaces 19, 19 a, 19 b of the driven member 4, 4 a, 4 b whereby alsothe second locking member 22 and, thereby, the freewheel 28 as an entityare unlocked. The spindle 1, 1 a, 1 b, together with the drive member 3,3 a, 3 b and the driven member 4, 4 a, 4 b, can now freely rotate andtransmit torque.

When the drive of the spindle 1, 1 a, 1 b rests, the axial cams 11, 11a, 11 b and the unlocking members 10, 10 a, 10 b are positioned inneutral position without any contact to the driven member 4, 4 a, 4 band the locking members 22. The latter are held in a locking position bythe spring elements 24. On rotating the spindle 1, 1 a, 1 b by hand, oneof the locking members 22 is engaged in the direction of the lockingposition and the other one in the unlocking direction, respectively,whereby the locking members 22 switch their function when the directionof rotation is changed. In this manner, a firm rotation connection tothe housing of the work tool is always present when the spindle 1, 1 a,1 b is rotated manually. This situation can be utilized for opening orclosing, or screwing on and off the drill chuck with one hand. Thereby,a double bush drill chuck is not required which is expensive and has tobe handled with both hands. Another advantage of the shaft lockingdevice is that a screw can be manually screwed in and out by using thework tool as an effective screw driver.

The specification incorporates by reference the entire disclosure ofGerman priority document 297 15 257.2 of Aug. 26, 1997, as well as ofInternational Application PCT/EP98/05432 of Aug. 26, 1998.

The present invention is, of course, in no way restricted to thespecific disclosure of the specification and drawings, but alsoencompasses any modifications within the scope of the appended claims.

1. A shaft locking device for a spindle (1,1 a,1 b) of a motor-driven,hand-guided work tool, said shaft locking device comprising: a spindle(1,1 a,1 b); a driven member (4,4 a,4 b) fixedly connected to saidspindle (1,1 a,1 b); a freewheel (28) having locking members (22); aring (23), fixedly connected to a housing, wherein said locking members(22) engage said ring (23) in both rotating directions of said spindle(1,1 a,1 b); a drive member (3,3 a,3 b) coaxially arranged to saidspindle (1,1 a,1 b) and provided with unlocking members (10,10 a,10 b),wherein said unlocking members (10,10 a,10 b) co-operate with saidlocking members (22) in order to release said locking members (22) whensaid drive member (3,3 a,3 b) is driven such that said driven member(4,4 a,4 b) is released from said ring (23) and is rotatable; saiddriven member (4,4 a,4 b) and said drive member (3,3 a,3 b) havingtorque-transmitting catch surfaces (18,18 a,18 b,19,19 a,19 b) for amotor-driven drive action of said spindle (1,1 a,1 b), whereby saidcatch surfaces (18,18 a,18 b,19,19 a,19 b) have a larger distance fromone another in a neutral position of said drive member (3,3 a,3 b) thana distance provided between said unlocking members (10,10 a,10 b) andrespectively associated ones of said locking members (22); said drivemember (3,3 a,3 b) having cams (11,11 a,11 b) that are spatiallyseparated from said unlocking member (10,10 a,10 b), wherein said cams(11,11 a,11 b) penetrate into said driven member (4,4 a,4 b), andwherein said drive member (3,3 a,3 b) is a toothed wheel (7,7 a,7 b)supported on said spindle (1); said driven member (4,4 a,4 b) havingcatch openings (30); wherein said torque-transmitting catch surfaces(18,18 a,19,19 a,19 b) are formed by cam surfaces (18,18 a,18 b) of saidcams (11,11 a,11 b) and by drive surfaces (19,19 a,19 b) of said catchopenings (30) facing said cam surfaces (18,18 a,18 b) in a respectiverotational direction of said spindle (1,1 a,1 b).
 2. A shaft lockingdevice according to claim 1, wherein said spindle (1, 1 a, 1 b) is aone-piece member and penetrates said driven member (4, 4 a, 4 b) andsaid drive member (3, 3 a, 3 b), wherein said spindle (1, 1 a, 1 b)serves as a support for said drive ember (3, 3 a, 3 b).
 3. A shaftlocking device according to claim 1, wherein said toothed wheel (7, 7 a,7 b) has plastic teeth (31).
 4. A shaft locking device according toclaim 1, wherein said cams (11) extend axially or radially into saidcatch openings (30) and wherein said catch openings (30) are embodied asring segments (17).
 5. A shaft locking device according to claim 1,wherein said cams (11 a, 11 b) extend axially or radially into saidcatch openings (30) and wherein said catch openings (30) are embodied asradial recesses (17 a, 17 b).
 6. A shaft locking device according toclaim 1, wherein said unlocking members (10, 10 a, 10 b) and the cams(11, 11 a, 11 b) are arranged concentrically to one another, whereinsaid unlocking members (10, 10 a, 10 b) embrace said driven member (4, 4a, 4 b) at a spacing.
 7. A shaft locking device according to claim 1,wherein said drive member (3, 3 a, 3 b) has at least two pairs ofsymmetrically embodied ones of said unlocking members (10, 10 a, 10 b)and said cams (11, 11 a, 11 b) wherein each one of said pairs has acommon center line (12) that is positioned at an equally spaced angle toneighboring ones of said center lines (12).
 8. A shaft locking deviceaccording to claim 1, wherein said driven member (4, 4 a, 4 b) isembodied as a deep-drawn sheet metal member (13) or as an extrudedmember (13 a) or as a thick disc (13 b).
 9. A shaft locking deviceaccording to claim 8, wherein said sheet metal member (13) or saidextruded member (13 a) or said disc (13 b) is provided withcircumferential cams (21) for said locking members (22).
 10. A shaftlocking device according to claim 8, further comprising a closing member(27, 27 b) fixedly attached to said driven member (4, 4 a, 4 b), whereinsaid closing member (27, 27 b) has a clearance-free contact to saidsheet metal member (13) or to a thick disc steel member (13 b) and hasaxial clearance to said locking members (22).
 11. A shaft locking deviceaccording to claim 1, wherein said cams (21) and associated one of saidlocking members (22) are arranged in pairs.
 12. A shaft locking deviceaccording to claim 1, further comprising spring elements (24) arrangedbetween said locking members (22).
 13. A shaft locking device accordingto claim 1, wherein said cam surfaces (18, 18 b) of said cams (11, 11 b)are radially aligned with said drive surfaces (19, 19 b) of said catchopenings (30).
 14. A shaft locking device according to claim 1, whereinsaid driven member (4, 4 a) is positive-lockingly connected to saidspindle (1, 1 a).
 15. A shaft locking device according to claim 1,wherein said driven member (4 b) is force-lockingly connected to saidspindle (1 b).